The pack method is used to communicate with the packer, a geometry manager that arranges the children of a owner by packing them in order around the edges of the owner.

In this port of Tk::pack it is normal to pack widgets one-at-a-time using the widget object to be packed to invoke a method call. This is a slight distortion of the original Tcl-Tk interface (which can handle lists of windows to one pack method call) but Tk reports that it has proven effective in practice.

The options consist of pairs of arguments that specify how to manage the slave. See "The packer algorithm" below for details on how the options are used by the packer. The following options are supported:

Specifies which side of the master the slave(s) will be packed against. Must be left, right, top, or bottom. Defaults to top.

If no in, after or before option is specified then slave will be inserted at the end of the packing list for its owner unless it is already managed by the packer (in which case it will be left where it is). If one of these options is specified then slave will be inserted at the specified point. If the slave are already managed by the geometry manager then any unspecified options for them retain their previous values rather than receiving default values.

If boolean has a true boolean value then propagation is enabled for $master, (see "Geometry propagation" below). If boolean has a false boolean value then propagation is disabled for $master. If boolean is omitted then the method returns 0 or 1 to indicate whether propagation is currently enabled for $master.

Returns a list of all of the slaves in the packing order for $master. The order of the slaves in the list is the same as their order in the packing order. If $master has no slaves then an empty list/string is returned in array/scalar context, respectively

For each master the packer maintains an ordered list of slaves called the packing list. The in, after, and before configuration options are used to specify the master for each slave and the slave's position in the packing list. If none of these options is given for a slave then the slave is added to the end of the packing list for its owner.

The packer arranges the slaves for a master by scanning the packing list in order. At the time it processes each slave, a rectangular area within the master is still unallocated. This area is called the cavity; for the first slave it is the entire area of the master.

For each slave the packer carries out the following steps:

The packer allocates a rectangular parcel for the slave along the side of the cavity given by the slave's side option. If the side is top or bottom then the width of the parcel is the width of the cavity and its height is the requested height of the slave plus the ipady and pady options. For the left or right side the height of the parcel is the height of the cavity and the width is the requested width of the slave plus the ipadx and padx options. The parcel may be enlarged further because of the expand option (see "Expansion" below)

The packer chooses the dimensions of the slave. The width will normally be the slave's requested width plus twice its ipadx option and the height will normally be the slave's requested height plus twice its ipady option. However, if the fill option is x or both then the width of the slave is expanded to fill the width of the parcel, minus twice the padx option. If the fill option is y or both then the height of the slave is expanded to fill the width of the parcel, minus twice the pady option.

The packer positions the slave over its parcel. If the slave is smaller than the parcel then the -anchor option determines where in the parcel the slave will be placed. If padx or pady is non-zero, then the given amount of external padding will always be left between the slave and the edges of the parcel.

Once a given slave has been packed, the area of its parcel is subtracted from the cavity, leaving a smaller rectangular cavity for the next slave. If a slave doesn't use all of its parcel, the unused space in the parcel will not be used by subsequent slaves. If the cavity should become too small to meet the needs of a slave then the slave will be given whatever space is left in the cavity. If the cavity shrinks to zero size, then all remaining slaves on the packing list will be unmapped from the screen until the master window becomes large enough to hold them again.

If a master window is so large that there will be extra space left over after all of its slaves have been packed, then the extra space is distributed uniformly among all of the slaves for which the expand option is set. Extra horizontal space is distributed among the expandable slaves whose side is left or right, and extra vertical space is distributed among the expandable slaves whose side is top or bottom.

The packer normally computes how large a master must be to just exactly meet the needs of its slaves, and it sets the requested width and height of the master to these dimensions. This causes geometry information to propagate up through a window hierarchy to a top-level window so that the entire sub-tree sizes itself to fit the needs of the leaf windows. However, the packPropagate method may be used to turn off propagation for one or more masters. If propagation is disabled then the packer will not set the requested width and height. This may be useful if, for example, you wish for a master window to have a fixed size that you specify.

If the master for a slave is not its owner then you must make sure that the slave is higher in the stacking order than the master. Otherwise the master will obscure the slave and it will appear as if the slave hasn't been packed correctly. The easiest way to make sure the slave is higher than the master is to create the master window first: the most recently created window will be highest in the stacking order. Or, you can use the bring_to_front and send_to_back methods to change the stacking order of either the master or the slave.